upsizing a breaker


Old 12-14-00, 01:00 AM
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I have a 15 amp breaker that runs into my shop. The breaker keeps tripping. I was told to just take out the 15 and put in a 20 and everything would be fine if my service had enough power to add it. My dad said to just add up all the breakers in the box and then compare them to the main. When I did that the breakers come up to 230 and my main is only a 200. Am I already over-extended power wise? Do I need to upgrade to 400 amp main? Any answers would be greatly appreciated. My wife wants a playhouse for the cats and it's too cold to do it without my heater!!!!
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Old 12-14-00, 03:07 AM
Join Date: Dec 1999
Location: Northeastern NC On The Albemarle Sound
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I'm not an electrician, but you need to check all of your shop wiring to make sure that it is at least 12/2 before upgrading to a 20 amp breaker.
If you have any of the smaller 14/2 on your shop circuit breaker, you cannot use more than a 15 amp, unless you upgrade all of the wiring to 12/2 also.
I would think that you already have 12/2, and going to a 20 amp will probably solve your problem.
A 200 amp service should be way more than adequate for your residential service. (Adding up breakers is not the way that you determine that.)
Good Luck!
Old 12-14-00, 06:52 AM
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First and most important: quit getting electrical information from your Dad!

As OldGuy said, check to see what gauge wire you have. Unfortunately, you need to check at every fixture on that circuit to make sure it is ALL 12 gauge. If you just check one place, you may miss the fact that you have a mixture of 12 and 14 gauge. I make the opposite assumption as OldGuy -- I think you probably have 14 gauge wire now.

Adding up the breakers in your box is completely meaningless. You might as well add up the number of doorknobs in your house and try to get some meaning from it.

The addition of breakers is meaningless for three reasons:
(1) The breakers are a combination of 120 volt and 240 volt circuits, so the numbers cannot be added. If you really want to do this, then count the 240 volt breakers as double the 120 volt breakers.
(2) The main breaker is 240 volts, so essentially the 200 amp breaker provides 400 amps of 120 volts.
(3) It is entirely acceptable to have 800 amps of 120 volt breakers in this panel. Load calculations always assume that not every circuit is loaded to maximum capacity at the same time.

Bottom line: If all the wire on this circuit is 12 gauge, go ahead and upgrade the breaker. If not, I always recommend gasoline and a match as a better alternative to using a 20-amp breaker on 14 gauge wire.
Old 12-14-00, 07:38 AM
Join Date: Dec 1999
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You're probably exactly right about the 14, but I was assuming (there I go again) that the shop had outlets on a 12/2 circuit, and that it was just the electric heater for the cats on that 15 amper that was popping it.
(Love that breaker/doorknob analogy!)LOL.
Now I know how to figure all of this high-tech electrical stuff. Let's see. I've got 36 doorknobs X 200 amps X 50 lbs water pressure X 68 degrees HVAC X two tv sets on cable = just enough juice to run this computer, and I don't know how to use 90% of it, either.
Later. OG


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